1. Field of Invention
Generally, the present invention relates to a glass envelope for a light emitting device, particularly to a flat glass envelope having an internal channel and a molded edge for facilitating attachments, for instance for supporting filters.
2. Description of Related Art
Light emitting devices or discharge lamps having an envelope with an enclosed, internal channel have been disclosed. Such envelopes are commonly formed from glass, are evacuated, and backfilled with an ionizable gas. Generally, internally channeled envelopes have been formed by cutting channels in a bottom glass plate. The channels may be formed by grinding, etching, sandblasting, or otherwise hollowing out a desired pattern in the plate. A top planar plate is then sealed, as with a sealing paste or a glass frit, to the bottom plate to form an enclosed channel.
Recently, a more efficient process and the glass envelope thereby produced has been disclosed in U.S. Pat. No. 5,834,888 (Allen et al.) and U.S. Pat. No. 5,858,046 (Allen et al.). The teachings of the above referenced patents are incorporated herein in their entirety. The method disclosed comprises successively delivering two sheets from a source of glass. A first glass sheet is delivered to a mold assembly having the desired channel forming pattern and a peripheral surface which the glass sheet overlies. The glass sheet may be caused to conform to the mold by the force of gravity, by drawing a vacuum, or by a combination of these forces. The second sheet is then delivered over the conformed, bottom sheet at a viscosity such that it hermetically seals to the raised portion of the bottom sheet, but does not sag into the channels of the mold. This provides a laminated, internally channeled, lightweight envelope in an efficient manner.
Still another method for forming discharge lighting devices has been disclosed in U.S. Patent Appl., having Ser. No. 09/308,554, and title xe2x80x9cMethod For Forming An Internally Channeled Glass Articlexe2x80x9d (Allen et al.), which is issued as U.S. Pat. No. 6,301,932, co-assigned to the instant assignee, and herein incorporated by reference. The method comprises delivering one sheet of molten glass from one source of glass. Briefly, upon exiting the rollers, first length of the molten glass ribbon is deposited upon the mold which is moved along a predetermined path, preferably a direction along the mold""s width; although the molten ribbon could be deposited in a direction along the mold""s length. Following the conformance of the first length to the mold cavity, through either gravity or vacuum forming or a combination of the two, the mold is thereafter moved back along a second predetermined path opposite the first direction and a second length of the molten glass is laid onto the first length of molten glass. In other words, second length of the molten glass ribbon is essentially folded over and onto first length of the molten glass ribbon.
Discharge lamps of the type described herein above find employment in such diverse areas as the automotive field, particularly in rear lighting applications, general lighting and liquid crystal display (LCD) backlighting. Often there exists the need to attach filters to such lighting devices. However, in order to accomplish such connections a separate device is needed which accommodates the discharge lamp and any other desired attachments.
Therefore, it is an object of the present invention to more easily facilitate the union of a discharge lamp with attachments, for example a filter, by eliminating the need for a separate device to affect this task.
It is also another object of the present invention to simplify discharge lamp product design.
According to the present invention, these and other objects and advantages are achieved in a glass envelope having an enclosed, internal channel and a molded edge for facilitating attachments directly to the glass envelope thereby eliminating the need for additional devices to connect said several components.
The molded edge could accommodate such diverse attachments as filters (i.e., diffusion, polarizing, and glare reducing), and liquid crystal display (LCD) screens, and masking components.
Lightweight, light-emitting sources or low-pressure discharge lamps may be formed from the glass envelopes of the present invention. The discharge lamps may be employed in the fields of automotive lighting, general lighting and LCD backlighting. Often filters are desired to modify or improve the source of light, i.e., direct light in different directions or render a brighter light. Since the present invention does not require a separate device to accommodate the lamp and filter because the filter can be attached directly to the glass envelope, there results a simplified product that provides more flexibility in terms of design options at the same time offering more cost effective options.
Furthermore, in addition to filters other attachments such as liquid crystal display screens may be attached to the glass envelope at the molded edge. It is well known that liquid crystal displays (LCD) require backlighting. The molded edge could be formed to accommodate an LCD screen, whereby the discharge lamp would serve as backlighting source.